1. Field of the Invention
The present invention relates to an optical device such as a camera system having an image blur prevention function, the camera system including an interchangeable lens and a camera main body that is equipped with the interchangeable lens.
2. Related Background Art
Up to now, some optical devices, such as a camera system that is structured by an interchangeable lens and a single-lens reflex camera that is equipped with the interchangeable lens in use, have an image blur prevention function that prevents a hand vibration at the time of photographing.
In each of the above-mentioned optical devices, both of an image blur detection means and an image blur correction optical system are disposed within the interchangeable lens so as to control the start and completion of the image blur correcting operation through the operation of an operation unit at a camera side.
A gyro sensor is generally employed as a vibration detection means which is disposed within the interchangeable lens. At least two gyro sensors are required for detection in a pitch direction and a yaw direction, and the gyro sensors remain expensive from the structural viewpoint. In the camera system such as the single-lens reflex camera, it is desirable that the costs of the interchangeable lenses be reduced by installing high-cost elements such as the above-mentioned sensors at the camera main body side.
The reason is that since several interchangeable lenses are prepared and interchanged in use, the reduction in the costs of the interchangeable lenses is greatly advantageous in the cost reduction as a total system.
From this viewpoint, Japanese Patent Application Laid-Open No. H06-250272 and so on have proposed an image blur prevention single-lens reflex camera system having a vibration detection means within the camera main body and an image blur correction optical system within the interchangeable lens.
It is possible that the camera-main body having the vibration detection means be equipped with a conventional interchangeable lens having a vibration prevention function with both of the above-mentioned vibration detection means and an image blur correction means (hereinafter referred to as “image stabilizer (IS) interchangeable lens”).
Also, since the IS interchangeable lens is designed under the assumption that the conventional camera main body that is not associated with the image blur prevention function at all (the camera main body having no vibration detection sensor) is installed as the camera main body with the IS interchangeable lens, an on/off changeover switch for the image blur prevention function is located at the IS interchangeable lens side.
Therefore, when the above-mentioned conventional IS interchangeable lens is installed in the camera main body having the image blur detection means within the camera main body, the on/off changeover switch for the image blur prevention function is located at both of the camera main body and the IS interchangeable lens.
It should be noted that the camera system disclosed in the above-mentioned Japanese Patent Application Laid-Open No. H06-250272 is not proposed taking into consideration control under the condition where the on/off changeover switch for the image blur prevention function is disposed at both of the camera main body and the IS interchangeable lens.